[PATCH net-next 2/2] net: Make skb_ext_put_mctp() idempotent
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: 2026-08-31 06:27:52
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
The MCTP flow extension can be released either when it is deleted from an skb or when the last skb holding the extension block is freed. Handle the release in __skb_ext_del(), which is currently missing, and make skb_ext_put_mctp() safe to call from both paths. This will let __skb_ext_put() release the MCTP key without checking whether the extension is present first, which is needed if we want to reuse skb_ext chunks area after skb scrubbing. Suggested-by: Florian Westphal <fw@strlen.de> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- net/core/skbuff.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index aa8b42c74f42..ab195b99c853 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c@@ -7248,8 +7248,11 @@ static void skb_ext_put_sp(struct sec_path *sp) #ifdef CONFIG_MCTP_FLOWS static void skb_ext_put_mctp(struct mctp_flow *flow) { - if (flow->key) - mctp_key_unref(flow->key); + if (!flow->key) + return; + + mctp_key_unref(flow->key); + flow->key = NULL; } #endif
@@ -7261,13 +7264,20 @@ void __skb_ext_del(struct sk_buff *skb, enum skb_ext_id id) if (skb->active_extensions == 0) { skb->extensions = NULL; __skb_ext_put(ext); -#ifdef CONFIG_XFRM - } else if (id == SKB_EXT_SEC_PATH && - refcount_read(&ext->refcnt) == 1) { + return; + } + + if (refcount_read(&ext->refcnt) > 1) + return; +#ifdef CONFIG_XFRM + if (id == SKB_EXT_SEC_PATH) skb_ext_put_sp(skb_ext_get_ptr(ext, SKB_EXT_SEC_PATH)); #endif - } +#ifdef CONFIG_MCTP_FLOWS + if (id == SKB_EXT_MCTP) + skb_ext_put_mctp(skb_ext_get_ptr(ext, SKB_EXT_MCTP)); +#endif } EXPORT_SYMBOL(__skb_ext_del);
--
2.43.0